High pressure, explosive-activated press



Aug? 176, 1960 E. w. LA RoccA ETAL 2,948,23

HIGH PRESSURE, EXPLOSIVEI-ACTIVATE DDDD SS J. IIIII'" 4 NNNNNNNN S.

E w v J o H N P E A R s ON 2.948323 inon PRESSURE, EXPLOSIVE-ACTIVATEDPRESS Edward W. La Rocca and John Pearson, China flake, Calift,assignors to the United States of America as represented by theSecretary of the Navy The invention described herein may be manufacturedand used by or for the Government of the United States of America forgovernmental purposes without the payment of any royalties thereon ortherefor.

This invention relates to a novel type of press and to a method forpress fo'rming materials.

In the press forming contemplated by this invention, very high pressuresare required. Hydraulic presses have been used in the past because theywere the only presses available capable of producing such highpressures. However, such presses are not capable of producing highenough pressures and loading rates to produce a pressformed metallicproduct of satisfactory strength. Further, such presses are bulky andexpensive.

It is therefore an object'of this invention to provide a method andapparatus for producing higher pressures than has heretofore beenpossible for press-forming objects.

Another object is to provide a method and apparatus for producing a morerapid loading rate than has been possible in the past in the art ofpress-forming.

Further objects are to pro'vide a relatively small and low cost pressfor press forming materials.

The above mentioned objects are accomplished by an explosive press inwhich a sample of material is compressed by a piston driven by anexplosion.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawing.

Referring to the drawing, the preferred embodiment, confining shells 1and 2 of steel are flat at one end and are provided with cavities in thefiat ends which hold the explosive 3 and 4. Said shells also containchannels which communicate between the explosive-containing cavities andthe exteriors of the shells and into which detonators 5 and 6 areplaced.

Adjacent the flat sides of the confining shells and loo'sely attachedthereto are outer plates 7 and 8 of steel which function to seal theexplosive-containing cavities and hold the explosive in place.

Pistons 9 and 10 of steel are adjoined to the plates 7 and 8respectively at one end as shown with their free ends extending into acylinder in a center plate 11 of steel to form a compartment or pressurechamber 12 wherein the material to be compressed is placed.

In operation, the material to be compressed is placed into the cylinderof the center plate and the pistons are placed into either end of thecylinder, firmly in contact with the sample. Then the outer plates 7 and8 are placed next to the pistons and the cavities in the confiningshells are filled with equal amounts of explosive and placed next to theouter plates. The assembled parts are weakly held in contact. Thendetonators 5 and 6 are placed in the shells and the apparatus is readyfor firing.

The two explosive charges are detonated simultanets Patent 'PatentedAug. 16,- 1960 2 ously, driving both pistons against the sample at once,resulting in very high pressures in the pressure chamber 12. Theco'nfining shells land 2 move in directions opposite to-their pistonsinto back-stops not shown.

Conventional electric detonators are preferred though other types may beused. Sand-bags. make good backstops, though various structures may beused.

It is, apparent that a large number of'explosives can be used includingliquids in containers and that the pressures obtained and their rates ofapplication are func tions of the particular explosive used, thequantities employed, the degree of confinement of the explosive and theparticular detonator employed, all of which can be varied at will. Highexplosives are preferred because they produce great pressures. It isobvious that the hole ,in the center plate into which the pistons fitmay have any cross-sectional shape, depending upon the shape desired inthe formed article. It is also obvious that one piston can have aparticular configuration sunk into its end and the other piston can havethe same configuration raised on its end so that when the two cometogether,

the configuration is pressed into the material.

Another obvious modification is to provide means for only one explosivecharge to compress the sample in a well in the center plate.

"Ihe outer plates may be recessed to hold the pistons, and aligning pinsor bolts may be used to assemble the system if desired.

The applications aforementioned have been directed to material formingbut the method and apparatus is also useful in bonding applications, forinstance, in the bonding of dissimilar metals in the manufacture ofthermocouples. Another important bonding application is in the formationof metal parts by compressing a metal powder. The pressures developedare sufiiciently high to form a coherent product from the powder,similar to that formed by sintering.

The method and apparatus have important applications in compressingsamples so that the properties of the compressed material may bestudied.

For many applications, only a small assembly a few inches long isrequired. Such an assembly is so cheaply made as to be expendable, asthe steel is cheap and the machining is simple. However, the inventionis not limited to small scale devices as the apparatus may be scaled upas required.

Small scale models of applicants device have been made and tested. Theshells were made in the shape of hemispherical capped cylinders, thehemisphere having a radius of about 1% inches, the cylinder being about1 /2 inches high and 2 /2 inches in diameter. The cavity for containingthe explosive was a cylinder about 1% inches in both height anddiameter, centrally positioned in the fiat end of the shell. The outerplates 7 and 8 had a four inch diameter and were about Vs inch thick.The center plate 11 had a four inch diameter and was one inch thick. Thepistons were about /1 inch in height and diameter and fitted fairlysmoothly in the cylinder in the center plate. The explosives used werestandard military explosives one containing 55.2 percent RDX, 40 percentTNT, 1.2 percent polyisobutylene, and 3.6 percent wax. RDX istrinitrotrimethylenetriamine; TNT is trinitrotoluene. Another explosiveused was one containing 78 percent RDX and nitrocellulose in equalamounts, and 22 percent inert plasticizer for the nitrocellulose.

Tests of the above systems gave pressures ranging from about 1.-5million p.s.i. As little as of a cubic inch of the TNT-containingexplosive aforementioned in each cavity gave pressures in excess of2,000,000 p.s.i. on the sample.

The press can be scaled up or down by substantially w proportionatelyenlarging or reducing the parts o'ver a pressure range of about 1-9million p.s.i. An increase in the amount of explosive will not produce asimple proportional increase in the pressure produced, but will producea greater pressure. The curve .of the amount of explosive used versusthe pressureexerted on the sample is believed to be exponential.

The present method and apparatus is capable of producing higherpressures and loading rates than has heretofore been possible.

With the higher pressures produced by the instant method and apparatus,it is possible to.cold-forrn metallic products without the applicationof heat. With the much more rapid application of pressure attained bythis invention, it is possible to form brittle materials of sufficientstrength to prevent crumbling and breaking. The forming operation occursso rapidly that the brittle materials do not have time to break up, noris the material allowed to break up as it is so closely confined. Thusbrittle materials in the press behave like ductile materials.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claim, .the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

A detonating explosive actuated high pressure press comprising twomovable, hollow, elongated, steel, confining shells, each of said shellshaving a fiat surface on one end thereof and a cavity in one end portionabutting said fiat surface, a high explosive charge filling said cavity,and a channel interconnecting said cavity with the exterior of the otherend of the shell, a pair of electric detonators, each of said detonatorsbeing disposed within a respective channel for detonating the explosivecharges, a pair of flat steel plates respectively abutting the flatsurfaces of said shells and enclosing said cavities, a pair of pistonsrespectively adjoined to said plates at one end thereof; a central platedisposed between said pair of plates in close proximate spaced relationtherewith and having a circular bore therethrough, each of said pistonsextending into said bore for sliding movement therein as the pair ofplates are suddenly moved toward each other and concurrentlytherewiththe shells are moved in opposite directions away from the pairof plates, the ends of said pistons together with the bore forming apressure chamber for receiving an object whereby the object iscompressed under momentarily applied high pressure and shaped to apredetermined configuration in response to the simultaneous detonationof the explosive charges.

References Cited in the file of this patent UNITED STATES PATENTS778,899 Ronay Jan. 3, 1905 2,132,148 Davis Oct. 4, 1938 2,149,641 TempleMar. 7, 1939 2,253,003 Whipple Aug. 19, 1941 2,472,120 Murphy June 7,1949 2,648,125 McKenna et a1. Aug. 11, 1953 2,815,698 Burrows Dec. 10,1957 2,872,682 Maier Feb. 10, 1959 2,893,279 Haskell et a1. July 7, 19592,905,080 Toulmin Sept. 22, 1959

